1. Field
This disclosure relates to hydrogen generation systems and, more particularly, to a compact integrated steam reformer apparatus for incorporation into compact steam reforming hydrogen generator systems.
2. General Background
A hydrogen generation unit (HGU) or system typically involves a steam reforming method that includes a combination of thermo-chemical processes that convert a fuel-steam mixture into a hydrogen-rich gas mixture typically composed of hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), water vapor (H2O) and other gases depending on the composition of the fuel feedstock. Typically, this mixture being produced is known as a reformate. For many applications this reformate stream is then passed to a hydrogen purification unit in which 60% to 90% of the hydrogen is separated into a relatively pure hydrogen stream (99+% H2) and an off-gas stream consisting of the other species in the reformate mixture.
A thermal cracking reactor may be used to decompose fuel into hydrogen and other compounds. This decomposition may be done in the presence of a catalyst but does not have to include catalysts. Thermal cracking-type reformers typically do not use water, and therefore also produce solid carbon or nitrogen if ammonia is utilized as the fuel. In reformers, hydrocarbon and organic fuels are typically reacted in the presence of water to produce hydrogen, carbon dioxide, and carbon monoxide. The most typical reformer used in industry is a steam reformer type reactor, but other reformers, which are known as auto-thermal reformers and partial oxidation reformers, can also use oxygen or air as a reactant. These reformers can be integrated with pre- and post-reactors such as steam generation and water gas shift (WGS) reactors to create a fuel processing system, and when integrated with hydrogen purification units, create a hydrogen generation system.
In energy applications such as fuel cell systems and hydrogen refueling stations, the efficiency of the hydrogen generation equipment can be critical to overall system economics when the energy value of hydrogen is converted into electricity. Similarly, reformers that are more compact with smaller foot prints and packaging flexibility are needed to reduce equipment cost and enhance the cost effectiveness of integrated systems. In addition, fuel cell and hydrogen refueling applications are not homogeneous in capacity. Some applications require only a few kilowatts and some require several hundred kilowatts. As a result, a reformer engineered for 25 kW applications must be completely re-engineered for a 2 kW or a 100 kW application. What the market needs are reformers with greater efficiency, enhanced compactness, and improved modularity.